The importance of mass transit in a functioning society increases as urbanization increases. In many locations, mass transit is the most efficient and quickest way of reaching a desired destination. Several cities would have a significant negative financial impact if their mass transit system were to be shut down.
Due to the size and usage of mass transit systems, security of these systems is difficult. Currently, security is provided by the presence of CCTV, guards or policeman who are tasked with preventing criminal activity. While such precautions have limited many risks associated with mass transit, further security improvements are both desired and necessary.